Our regulatory assets and liabilities result from our application of the provisions of Topic 980 and are reflected on our balance sheet. Current regulatory assets are included in Exchange gas offset and Prepayments and other. Current regulatory liabilities are included in Exchange gas offset. These balances are presented on our balance sheet on a gross basis and are recoverable or refundable over various periods. Below are the details of our regulatory assets and liabilities as of December 31, 2014 and 2013:



	2014		2013
	(Thousands of Dollars)
Current regulatory assets:
Environmental costs	$	1,300	$	1,300
Levelized depreciation	1,999		—
Total current regulatory assets	3,299		1,300
Noncurrent regulatory assets:
Environmental costs	2,109		2,843
Grossed-up deferred taxes on equity funds used during construction	14,567		15,325
Levelized depreciation	29,775		33,261
Asset retirement obligations, net	3,472		6,712
Total noncurrent regulatory assets	49,923		58,141
Total regulatory assets	$	53,222	$	59,441
Current regulatory liabilities:
Fuel recovery	$	4,004	$	638
Noncurrent regulatory liabilities:
Postretirement benefits	23,375		19,047
Other	—		205
Total noncurrent regulatory liabilities	23,375		19,252
Total regulatory liabilities	$	27,379	$	19,890